1. Field of the Invention
The present invention generally relates to a sample supporting device adopted to a ventilation-characteristics measuring apparatus, and, more particularly, to a cigarette supporting device used for measuring the ventilation-characteristics of a cigarette, and also to a ventilation-characteristics measuring apparatus employing such a cigarette supporting device.
2. Description of the Related Art
A ventilation-characteristics measuring apparatus is to measure a flow rate of air (i.e., a ratio of an airintake amount to a dilution amount) sucked into a sample held in an airtight chamber, from the exterior of the airtight chamber, as well as a ventilation resistance of the sample, when sucking the inside air of the airtight chamber at a predetermined flow rate.
For supporting such a light-weight and soft sample as a cigarette in the ventilation-characteristics measuring apparatus, there is used a relatively thin-walled and soft member such as a tube formed by a latex dipping method. Moreover, in an automatic measuring apparatus for measuring ventilation characteristics of a sample continuously, the support for the sample is released generally by vacuum suction because this sample supporting member serves to support and release the sample and also serves as a separator in an airtight chamber (a separator for maintaining airtightness).
FIG. 1 shows one of conventional sample supporting devices employed in a conventional ventilation-characteristics measuring apparatus. An airtight chamber 1 is partitioned into first, second and third airtight chambers 1A, 1B and 1C in this order from above by means of flanges 2, 3 and 4. A sample stopper 5 movable in a direction of an arrow 40 is provided below the third airtight chamber 1C. In the state of FIG. 1, the stopper 5 is in operation to stop dropping of a cigarette 9. In the flanges 2, 3 and 4, suction paths 2A, 3A and 4A are formed. A holding ring 7 for mounting a sample supporting member 6 is fixed to the inside end of each of the flanges 2, 3 and 4. Each holding ring 7 is formed with a suction hole 7a communicating with the suction path 2, 3 or 4. All of the flanges--holding ring 7--sample supporting member 6 combinations are in just the same relationship. FIG. 2 shows one member of such combinations (an enlarged view).
FIGS. 3A and 3B are sectional views showing the shape of the conventional sample supporting member before mounting and that after mounting respectively. The sample supporting member is integrally formed from a soft and thin-walled synthetic resin material such as a tube formed by a latex dipping method. Before mounting, it is cylindrical (FIG. 3A), while after mounting, it is of a shape with both ends thereof bent in .angle.-form with respect to a vertical axis (FIG. 3B).
As is seen from FIG. 2, the sample supporting member 6 is inserted into a central, sample supporting hole 7B of the holding ring 7 in substantially close contact with the hole. Both bent ends of the sample supporting member 6 are stretched out into close contact with the outer periphery of the holding ring 7, whereby it is mounted to the holding ring.
Further, the holding ring 7 has a groove 7C formed in the outer periphery thereof. An O-ring 8 is fitted in the groove 7C to thereby prevent the sample supporting member 6 from dropping from the holding ring 7.
In the measurement of ventilation-characteristics, the sample 9 is inserted onto the sample supporting hole 7B and its longitudinal position is defined by the sample stopper 5. At the time of the sample insertion, a negative pressure is applied to the outer periphery of the sample supporting member 6 from the exterior through the suction hole 7A. By virtue of the negative pressure, the sample supporting member 6 is brought into close contact with the inner wall of the holding ring 7, resulting in its diameter becoming a little larger than the outside diameter of the sample 9, thus permitting easy insertion of the sample into the sample supporting hole 7B. Then, upon removal of the negative pressure, the inner wall of the sample supporting member 6 expands inwards by virtue of rubbery elasticity thereof as shown in FIG. 2. That is, the diameter of the sample supporting hole 7B is reduced. Consequently, the sample 9 of a light weight is supported within the airtight chamber 9 by means of the elastic force of each sample supporting member 6. In this case, the interior of the airtight chamber 1 is partitioned into three airtight chambers 1A, 1B and 1C by three sample supporting member 6. After the end of the measurement, if a negative pressure is applied again to the outer periphery of the sample supporting member 6 through the suction paths 2A, 3A and 4A, the sample 9 will fall to the exterior of the airtight chamber 1, downwards in FIG. 1.
In the conventional sample supporting device, the support for the sample 9 by the sample supporting member 6 is effected at the inner wall surface of the sample supporting member expanded in the form of a curved surface, that is, this contact is established by "face contact". As a result, with respect to a sample having fine air-previous characteristic throughout the outer periphery thereof such as, for example, a cigarette, in the case of measuring an air intake quantity at various points of the cigarette in plural airtight chambers, it is practically impossible to obtain highly accurate measuring values, because the face contact portion is closed during the measurement. This has been a drawback.
Also in mneasuring ventilation resistance of a cigarette, there has been the problem that highly accurate measured values cannot be obtained.
The present invention has been accomplished in view of the above-mentioned drawbacks. An object of the present invention is to provide a sample supporting device for a ventilation-characteristics measuring apparatus, capable of holding a sample at a minimum contact area to permit a highly accurate measurement of ventilation characteristics of the sample.
Another object of the present invention is to provide a ventilation-characteristics measuring apparatus capable of measuring ventilation characteristics of a sample with a high accuracy.